1. Field
The disclosed concept relates generally to containers and, more particularly, to can ends having retort resistant end panels. The disclosed concept also relates to tooling and associated methods for providing such can ends.
2. Background Information
Metallic containers (e.g., cans) for holding products such as, for example, food and beverages, are typically provided with an easy open can end on which a pull tab is attached (e.g., without limitation, riveted) to a tear strip or severable panel. The severable panel is defined by a scoreline in the exterior surface (e.g., public side) of the can end. The pull tab is structured to be lifted and/or pulled to sever the scoreline and deflect and/or remove the severable panel, thereby creating an opening for dispensing the contents of the can.
When the can end is made, it originates as a can end shell, which is formed from a sheet metal product (e.g., without limitation, sheet aluminum; sheet steel). The shell is then conveyed to a conversion press, which has a number of successive tool stations. As the shell advances from one tool station to the next, conversion operations such as, for example and without limitation, rivet forming, paneling, scoring, embossing, and tab staking, are performed until the shell is fully converted into the desired can end and is discharged from the press.
In the can making industry, large volumes of metal are required in order to manufacture a considerable number of cans. Thus, an ongoing objective in the industry is to reduce the amount of metal that is consumed. Efforts are constantly being made, therefore, to reduce the thickness or gauge (sometimes referred to as “down-gauging”) of the stock material from which can ends, tabs, and can bodies are made. However, as less material (e.g., thinner gauge) is used, problems arise that require the development of unique solutions. By way of example, a common problem associated with can ends for food cans is that they are subject to pressure changes associated with processing the food product within the can. More specifically, substances (e.g., without limitation, liquid; food; any other suitable substance) are commonly packaged in vacuum sealed cans. For example, a typical process for vacuum packaging food in metal cans includes filling the cans with uncooked food, sealing the can end or lid on the can and placing the can into an oven. This process is referred to as a retort process. As the food is cooked, pressure builds within the can. Then the can is cooled. Thus, the retort process induces internal (i.e., positive) pressure, followed by external (i.e., negative) pressure. The combination of the internal and external pressures induces stress on the end panel of the can end. Accordingly, for can ends and shell designs made from material having a reduced gauge or reduced blank size, such pressures and stresses tend to cause the end panel to permanently deform and/or wrinkle.
FIGS. 1A and 1B, for example, show an easy open can end 2 before (FIG. 1A) and after (FIG. 1B) the retort process. The can end 2 includes an opener (e.g., without limitation, pull tab 4), which is attached (e.g., without limitation, riveted) to a tear strip or severable panel 6. The severable panel 6 is defined by a scoreline 8 in the exterior surface 10 (e.g., public side, shown) of the can end 2. The pull tab 4 is structured to be lifted and/or pulled to sever the scoreline 8 and deflect and/or remove the severable panel 6, thereby creating an opening for dispensing the contents of the can (not shown in the top plan views of FIGS. 1A and 1B). The can end 2 in the example of FIGS. 1A and 1B is a 300 diameter end 2, and the panel 6 includes an up-panel 12 consisting of an arcuate raised area that extends outwardly from the public side 10 of the panel 6 and around the perimeter of the panel 6. As shown in FIG. 1B, the stresses caused by the internal and external pressures associated with the retort cooking process cause the panel 6 to permanently deform (e.g., without limitation, wrinkle) See, for example, the wrinkles and deformed sections generally indicated by reference 14 in FIG. 1B.
There is, therefore, room for improvement in can ends, and in tooling and methods for providing such can ends.